Proboscidea is an order including only one family, Elephantidae or the elephants, with 3 species: the Savannah Elephant, the Forest Elephant and the Asian Elephant (formerly known as the Indian Elephant). During the period of the ice age there were more, now extinct species, including the elephant-like mammoth and mastodont and the "shovel tuskers", the platybelodon and amebelodon.

Elephants are the largest living land mammals. At birth it is common for an elephant calf to weigh 100 kg (225 pounds). It takes 20 to 22 months for a baby elephant to develop, the longest gestation period of any land animal. The largest elephant ever recorded was a male shot in Angola in 1974, that weighed 12 tonnes (13.5 tons).

An elephant's most obvious characteristic is the trunk, a much elongated combination of nose and upper lip, which can be used to grab objects such as food. Elephants also have tusks, large teeth coming out of their upper jaws. Elephant tusks are the major source of ivory, but because of the increased rarity of elephants, hunting and ivory trade is now illegal.

Elephants are vegetarians, spending 16 hours a day collecting plant food from all levels. Their diet is at least 50% grasses, supplemented with leaves, twigs, bark, roots, and small amounts of fruits, seeds and flowers. Because elephants only use 40% of what they eat they have to make up for their digestive system's lack of efficiency in volume. An adult elephant can consume 300 to 600 pounds of food a day. 60% of that food leaves the elephant's body undigested.

Walking at a normal pace an elephant covers about 2 to 4 miles an hour but they can reach 24 miles an hour at full speed.

It has long been known that African and Asian elephants were separate species. African elephants tend to be larger than the Asian species (up to 4m high and 7500kg) and have bigger ears (which are rich in veins and thought to help in cooling off the blood in the hotter African climate). Female African elephants have tusks, while female Asian Elephants do not. African elephants have a dipped back, as compared with the Asian species, and have two "fingers" at the tip of their trunks, as opposed to only one.

Poaching has had some unexpected consequences on elephant anatomy as well. African ivory hunters, by killing only tusked elephants, have given a much larger chance of mating to elephants with small tusks or no tusks at all. The propagation of the absent-tusk gene has resulted in the birth of large numbers of tuskless elephants, now approaching 30% in some populations (compare with a rate of about 1% in 1930). Tusklessness, once a very rare genetic abnormality, has become a widespread hereditary trait.

Elephants have been used in various capacities by humans. War elephants were used by armies in the Indian sub-continent, and by the Persian empire. This use was adopted by Hellenistic Ptolemaic and Seleucid kingdoms. The Carthaginian general Hannibal took elephants across the Alps when he was fighting the Romans. Hannibal brought too few elephants to be of much military use, although his horse cavalry was quite successful. Hannibal probably used a now extinct third African species, the North African elephant, smaller than its two southern cousins.

In the wild, elephants exhibit complex social behavior and strong family bonds. Most females will stay with their original natal group for a lifetime. Social hierarchy in calf-cow groups is based on size and age, with the largest and oldest females at the top and the smallest and youngest coming in last. Adolescent males determine their own ranking order through head-butting contests, where strength and temperament are as important as size and age. They communicate with very low and long-ranging subsonic tones.

A recent theory holds that elephants, which share an ancestor with sea cows, evolved from animals which spent most of their time in the water or even under water, using their trunks like snorkels for breathing. It has been recently discovered that the species can still swim using their trunks in that manner.